Generally, a viscosity of an automotive transmission fluid is about 200 times higher at a very low temperature of −35 to −25° C. than a corresponding viscosity at a normal temperature. As a result, a valve sliding resistance force of a valve body controlling an oil pressure may be very large and a rough operation of a valve may occur due to micro residual burrs, scratches, or the like at a bore of the valve body that does not occur at the normal temperature.
In particular, due to a decrease in a line pressure or a non-generation of a pressure upon sliding of a regulator valve controlling the line pressure, a transmission clutch or a transmission brake may not be supplied with an adequate oil pressure. In this case, a hybrid vehicle has a problem in that a motor speed may diverge or the engine and the motor may not be combined with each other upon an initial launch of the hybrid vehicle.
The present disclosure relates to a control method for solving an adverse line pressure situation of a hybrid vehicle at a time of the very low temperature by controlling an electric oil pump (EOP) and a solenoid valve, when the adequate line pressure may not be generated.
The contents described as the related art have been provided only for assisting in the understanding of the background of the present disclosure and should not be considered as corresponding to the related art known to those skilled in the art.